Women who engage in regular vigorous physical activity lower their risk for psoriasis by 25% to 30%, a large prospective study found.

Action Points

Physical activity has been found to be protective against several diseases tied to high levels of systemic inflammation, but the effects on psoriasis have not been established.

In this study of female nurses, vigorous physical activity, but not walking, was independently associated with a decreased risk of psoriasis -- a finding that remained significant after adjustment for body mass index.

Women who engage in regular vigorous physical activity lower their risk for psoriasis by 25% to 30%, a large prospective study found.

After adjustment for age, alcohol use, and smoking, women in the highest quintile for total physical activity had a relative risk for developing psoriasis of 0.72 (95% CI 0.59 to 0.89, P=0.09) compared with those in the lowest quintile, according to Abrar A. Qureshi, MD, and colleagues from Harvard University.

And for those in the top quintile of performing vigorous physical activity in particular, the relative risk -- after adjusting for body mass index as well as other confounders -- was 0.73 (95% CI 0.60 to 0.90, P=0.009), the researchers reported online in the Archives of Dermatology.

Physical activity has been shown to be protective against a number of diseases linked with high levels of systemic inflammation, such as coronary artery disease and type 2 diabetes, but the effects on psoriasis have not been established.

To examine this, Qureshi's group evaluated outcomes for 86,665 women enrolled in the Nurses' Health Study who completed detailed questionnaires on their time spent each week in various leisure activities such as walking, running, and swimming.

During 14 years of follow-up, there were 1,026 new cases of psoriasis, for an incidence rate of 86 per 100,000 person-years.

Degree of physical activity was assessed according to metabolic equivalent task (MET) values, with the highest quintile having 31.9 or more MET hours and the lowest having 0.2 to 3.8 MET hours per week.

The relative risks for psoriasis among women in the middle quintiles were not significantly reduced, but the overall pattern was a decrease in risk with greater activity.

The most pronounced risk reduction was seen in women who reported running for at least an hour each week. Their relative risk, after adjustment for age, smoking, alcohol use, other types of vigorous activity, and walking, was 0.37 (95% CI 0.19 to 0.72, P=0.002).

After further adjustment for body mass index, runners had a relative risk of 0.45 (95% CI 0.23 to 0.87, P=0.02).

For women who did aerobic exercise for 4 or more hours each week, the relative risk was 0.54 (95% CI 0.33 to 0.88, P=0.03). After adjustment for body mass index, the risk in this group was 0.59 (95% CI 0.36 to 0.96, P=0.2).

Other types of physical activity such as walking, swimming, and bicycling did not lower the risk.

In a subset of women whose self-reported psoriasis was confirmed by their responses to the validated psoriasis screening tool questionnaire, the relative risk was 0.62 (95% CI 0.46 to 0.84, P=0.001) with 31.9 or more MET hours per week.

Among this group, the risk was 0.57 (95% CI 0.43 to 0.76, P=0.002) for 20.9 MET hours of vigorous physical activity each week, which was equivalent to 2 hours of running or 3 hours of swimming weekly.

Although further research will be needed to fully explicate the mechanisms by which vigorous activity influences the risk of psoriasis, effects on inflammation are "biologically plausible," according to the authors.

Specifically, physical activity can raise levels of anti-inflammatory cytokines such as adiponectin, while decreasing levels of pro-inflammatory markers such as leptin and tumor necrosis factor.

Further contributing could be the beneficial effects of exercise on mood and stress lowering, the researchers noted.

Limitations of the study included the self-report of psoriasis and the possibility of unmeasured confounders. For instance, time spent outdoors during physical activity was not measured, and ultraviolet exposure could have had protective effects.

However, the authors considered this an unlikely confounder, because walking for 4 hours outdoors had no effect on risk.

"In addition to providing other health benefits, participation in vigorous exercise may represent a new preventive measure for women at high risk of developing psoriasis," they concluded.

Qureshi is a consultant to Novartis and the Centers for Disease Control and Prevention.

Reviewed by Zalman S. Agus, MD Emeritus Professor, Perelman School of Medicine at the University of Pennsylvania and Dorothy Caputo, MA, BSN, RN, Nurse Planner

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